European patent no. 0 720 551 B1 BOSCH shows a typical model of such a traditional unit for slip-regulated braking systems of motor vehicles. This unit has a valve block of light metal with multiple stepped receiving holes for the hydraulic part of electromagnetically operated valves. In one step of the receiving hole, in each case this hydraulic part is inserted and fixed on the valve block by calking. A pressure-tight valve dome, which contains the magnetically active elements such as the armature and magnet core of the hydraulic part, projects above the valve block. A separately manufactured electrical part of the valve, which is plugged onto the valve dome, has an electrical coil which surrounds the valve dome, and a housing, which conducts magnetic flux, and in which, on the side facing the valve block, a soft magnetic ring disc to conduct the magnetic flux is received.
The hydraulic/electronic ABS/ASR/ESC closed-loop control unit TEVES MK60 (ASR (drive slip regulation) or FDR (Fahrdynamikregelung)=driving dynamics closed-loop control, e.g. ESC=electronic stability control), which has a central hydraulic block of aluminium with electromagnetically switching valves and an integrated hydraulic fluid pump, represents a comparable arrangement. This pump is operated by an electric motor which is attached to one side of the hydraulic block. On the opposite side of the hydraulic block, there is a separate coil holder for the electromagnetically switching valves, including the associated, likewise separately manufactured open-loop/closed-loop control electronics. The coil holder is put onto the valves by means of a so-called “magnetic plug”. The valves are practically divided into two: a hydraulic/mechanical part which is incorporated in the central hydraulic block, and a valve coil which is contained in/on the housing of the associated open-loop/closed-loop control electronics. When the open-loop/closed-loop control electronics are plugged onto the hydraulic/mechanical part of the valves in/on the central hydraulic block, the valves become functional. The electromagnetically switching valves make it possible to modulate the brake pressures. An outlet valve and an inlet valve, with non-return valve connected in parallel, are associated with each brake circuit. The central hydraulic block has two fluid connections for connection to a main brake cylinder which is operated by the brake pedal, and four brake line connections which each lead to a wheel brake. The pump which is integrated into the hydraulic block is a dual-circuit reciprocating pump, which conveys brake fluid from a low-pressure reservoir into the appropriate brake circuits. It thus replaces the brake fluid which is withdrawn from the brake circuits during ABS regulation. During active closed-loop control processes (e.g. ASR or ESC), which run without the brake pedal being operated by a driver, the pump makes the fluid volume which is required in the pressure buildup phase available in the brake circuits.
From the wheel rotational speeds which are captured on the four wheels by means of appropriate sensors, and other information (e.g. vehicle yaw rate, steering wheel angle, hydraulic pressure in the braking system, brake light switches, etc.), the open-loop/closed-loop control electronics determine the control signals for the actuators (electromagnetically switching valves, hydraulic pump, engine management, etc.). The aim is to increase the driving stability of the vehicle during braking—even on bends—to maintain the maneuverability of the vehicle even in critical braking situations—e.g. different coefficients of friction of the road surface—and if possible to use the existing braking distance optimally, to prevent racing of the driving wheels of the vehicle, and to improve the transverse dynamic handling properties of the vehicle independently of pedal operation. Finally, the control noises, the pedal vibration (“pedal feel”) and control convenience should also be optimised.
It is common to all known designs that the construction and assembly of such hydraulic/electronic ABS/ASR/ESC closed-loop control units is very complicated. Additionally, these closed-loop control units are very heavy and bulky despite the use of light metal for the hydraulic block, not least because of the large number of fluid on-off valves and the required high fluid pump power. There is also the constant pressure from the vehicle manufacturers on the costs of components and systems from their supplier partners.
WO 97/29310 A1, US 2002/0032093 A1 and DE 10344662 A1 show brake, transmission or steering units or their valve modules with ceramic components. These concern the carrier board for the electronics and/or valve elements.
DE 60204806 T2, U.S. Pat. No. 2,871,878 A, U.S. Pat. No. 3,631,881 A and
U.S. Pat. No. 4,458,841 A show valve modules which are in sandwich construction, and in which the unit bodies consist of boards which are connected to each other and have fluid on-off valves, hydraulic connecting lines between the fluid on-off valves being incorporated in the boards. The boards consist of metal or plastic.
U.S. Pat. No. 5,606,201 A, EP 0 309 986 A1 and DD 282 513 A5 show ceramic components which have a fluid line and are also in the form of electronic carriers. From DD 2825513 A5, ceramic boards which are connected to each other and have incorporated hydraulic connecting lines can be taken.
DE 81 18 656 U1 and DE 26 48 915 A1 show ceramic valve housings.